I am all for students dropping by my office hours, scheduling appointments at other times, or asking questions via email or IM.
However, if you ever pull a stunt like showing up in my office to conduct a three-hour debate over my grading policy you can rest assured that the one thing you shouldn’t expect as a consequence is more lenient grading from that point forward. Moreover, I have a very strong suspicion that most college professors would take the same position.